Nonwoven articles are found in every aspect of modern life, from diapers and adult incontinence devices to personal care items and bathroom tissue to baby wipes. Most if not all of these items come in contact with human skin during the normal course of their use.
It is a constant struggle to make these items softer, silkier and more pleasant to use without diminishing the absorptivity of the nonwoven web and thus not interfere with the intended utility of the article. One such invention, U.S. Pat. No. 5,607,760 (Donald Roe), relates to a lotion coated onto the topsheet of the disposable diaper or similar device. The lotion is transferred to the wearer's skin and thus reduces the adherence of bowel movements, while affording the wearer enhanced skin softness. One challenge of such an invention is to maintain the lotion at or near the surface of the web where it will be available for deposition onto the skin.
Generally lotions or emollients used in the treatment of skin are highly mobile, oil-like materials capable of easily migrating through a web. Migration of the lotion or oil can have a number of detrimental effects in that it will no longer be available for deposition or may adversely affect the absorption/transmittance of moisture (e.g. urine) into or through the supporting web and/or interferes with adhesion of converting adhesives. To overcome the migration problem U.S. Pat. No. 5,525,345 (Warner et al.) relies on a semi-solid lotion capable of melting at or around body temperature. Described in this reference are the use of synthetic type waxes and low molecular weight ethoxylates to afford the semi-solid consistency of the formulation. The semi-solid state will prevent the lotion from migrating until warmed to body temperature when it will liquefy and be deposited onto the skin.
In the above patents the inventors have touched upon the detrimental effects of having high loadings (the amount of lotion or emollient applied to the web) in the loss of tensile strength and reduction in caliper of the sheet. Typically in the industry thickness is correlated to softness and absorptivity.
Thus, there is still a long felt need in the marketplace for a treated web with high loadings of liquid or semi-solid lotions or emollients with good softness and feel while not interfering with water penetration/absorption or change in the thickness of the article. Ideally these emollient-treated webs may be undetectable to the casual user (unless intentionally made to stand out), but capable of delivering the lotion to the skin by action of an aqueous medium (e.g. urine or water) or other triggered release mechanisms such as friction.